The present invention relates to the art of belt restraint assemblies and, in particular, to compression type restraint mechanisms used as restraint harness adjusters.
It is known in the art of seat belt restraint systems to provide restraint harness adjustment assemblies in which a compression type restraint means or brake is used to prevent the belt from being pulled out of the adjustment under a load. Generally a restraint adjuster or slide buckle is a device which forms part of a seat belt system and has the function of providing an adjustment means for the length of the belt, harness, or webbing. The device usually includes a restraining means or brake which has a pair of cooperating jaw members mounted in operative relationship to a guide means. The jaw members can be movable in a housing in one direction toward a clamping position in which the jaw members, with the belt therebetween, are wedged together to retain the belt in a fixed position. When the belt is moved in the opposite direction between the jaw members, they are separable in order to allow the belt to freely move therethrough.
One of the devices known in the art is disclosed in U.S. Pat. No. 3,587,140 to Gaylord, et al. issued June 28, 1971, which describes an adjuster assembly that is intended to prevent accidental release of the belt or web so that the adjuster is able to support a predetermined load, and provide a means whereby the length of the belt can be quickly adjusted in either direction. Specifically, resilient means urge two plates to tightly grip the branch of the belt between them up to a predetermined load by the tension of springs attached to the plates, but when one of the gripping plates is pulled from the other, the clamping grip can be disengaged from the belt so as to permit the adjustment of the belt in the direction of pull by the load. Gripping elements on the opposing surfaces of the belt in the Gaylord, et al. patent are unidirectional, in order to resist movement in the direction of the load, but permit adjustment in the opposite direction. The assembly cover of Gaylord is considered quite complex and certain disadvantages have been realized as a result of such complexity.
More recently, U.S. Pat. No. 3,950,826 to Knoll, et al. discloses a seat belt assembly which overcomes many of the Gaylord, et al. problems and includes guide rods which are spaced apart fixed bearing surfaces assembled to side members of a support, and which are so located as to limit the forward travel of clamping members. There is a sloping surface on the clamping members which cam against the guide rods so that vertical displacement of the clamping members takes place. Elongated slots in the guide plates provide vertical freedom so that the clamping members tend to come together under the influence of the force provided by springs. The belt is free to move within the restraint adjuster in one direction without any need to utilize the release means provided, and the clamping means automatically reclamps itself against the belt when the adjustment is completed.
The Knoll, et al. disclosure provides for gripping surfaces on the clamping jaws which consists of rubber (or equivalent) pads whose function is to maintain strong pinching action without allowing fraying of the belt as would generally occur when metallic serrated surfaces, such as those of Gaylord, et al. are used. However, certain problems are incurred in the use of the rubber or similar material braking pads in that webbing slippage can occur at very cold temperatures. Other problems associated with using a rubber friction pad are that the rubber suffers deterioration with time and aging which relates to the nature of the rubber molecule--a long chain-like structure consisting of many smaller molecules joined together. Since it is believed that the bonds between these molecules are particularly susceptible to chemical reaction, at least three principle types of reactions are associated with such deterioration. The first one is scission in which the molecular bonds are cut dividing the chain into smaller segments. Ozone and ultraviolet light as well as radiation cause deterioration of this type. Another type of deterioration caused principally by heat and oxygen is cross-linking, which is an oxidation process whereby additional intermolecular bonds are formed. A third type of deterioration is modification of side groups which can change the complex in the weaker fringe areas of the molecular construction due to chemical reaction. Moisture, for example, could promote this type of activity.
These three types of reaction usually occur concurrently and in varying degrees. It is noted that all mechanisms by which rubber deteriorates, with time, are attributable to environmental conditions both in storage and actual service.
Accordingly, it is an object of the present invention to overcome these and other problems associated with providing a braking or restraint surface for a compression type restraint means in a belt assembly apparatus.